Permanent magnet synchronous motors (PMSMs), brushless direct current motors (BLDCs), switched reluctance motors, stepper motors, and induction motors represent types of motors that can be controlled using a field-oriented control (FOC) technique. These types of motors typically include a rotating rotor and a stationary stator. These motors are often powered by an inverter that converts a direct current (DC) input into an alternating current (AC) output.
In an FOC technique, various outputs of the inverter are controlled in order to adjust operation of a motor. “Sensorless” FOC refers to an approach where one or more characteristics of the motor, such as motor speed or rotor position, are derived rather than being measured directly using sensors on the motor. In some sensorless FOC techniques, the voltage on a DC bus providing the DC input to the inverter and samples of two-phase or three-phase currents provided by the inverter are used. In other sensorless FOC techniques, current on the DC bus is measured and used since the DC bus' current includes three-phase current information. As these approaches use current samples, they generally require the use of one or more analog-to-digital converters and one or more operational amplifiers to capture the current samples.